The biggest issue is dealing with lack of rigidity.
Get the machine is rigid as possible, especially Z-axis is very important for the success rate.
You can go shallow DOC as you mention, trade-off is machining time.
No need either to carve the whole inside, a cutout is enough. (as you say)
If you use a 3mm bit and say 9mm wide channel for cutout you can use the combination of 2D Adaptive for roughing and a plain Contour for finishing.
With 2D Adaptive you can go deeper per pass (try 1,5mm or 3mm DoC) but keep WoC (Width of cut) shallow. The bit make a helical plunge to depth then start doing slices.
The benefit of this is primarely:
- You use a larger part of the cutter edge = less wear
- The 9mm wide channel / tool path make chip clearing easy
Also see this - https://www.youtube.com/watch?v=8D8livGvnUY